This invention relates to a cis-bicyclo[3.3.0]octylidene derivative represented by the formula: ##STR4## wherein R.sup.1 is a hydrogen atom or an alkyl group; R.sup.2 is a hydrogen atom or a protective group for hydroxyl group; and Y is ##STR5## where R.sup.3 is a hydrogen atom or a protective group for hydroxyl group; R.sup.4 is a hydrogen atom or a straight, branched or cyclic alkyl group, alkenyl group or alkynyl group; and X is a group represented by CH.dbd.CH or C.tbd.C.
The cis-bicyclo[3.3.0]octylidene derivative represented by the above formula (I) obtained according to this invention can be subjected to deprotection of the primary hydroxyl group, oxidation, elongation of an .omega.-chain by utilizing the Wittig reaction and reduction of a 15-position carbonyl group (prostaglandine numbering) for deprotection, or deprotection of the protective group and hydrolysis of the ester to be led to a carbacycline which is useful as a therapeutic or prophylactic of various circulatory diseases (see Reference examples shown below).
In the prior art, most of the methods for preparation of a 5-E-exo-trisubstituted olefin such as a cis-bicyclo[3.3.0]octylidene derivative represented by the above formula (I) utilize the Wittig reaction as shown below, and they are disclosed in, for example, M. Shibasaki, J. Ueda and S. Ikegami, Tetrahedron Lett., 433 (1979); D. R. Morton, Jr. and F. C. Brokaw, J. Org. Chem., 44, 2880 (1979); W. Skuballa and H. Vorbruggen, Angew. Chem. Int. Ed. Engl., 20, 1046 (1981); Y. Konishi, M. Kawamura, Y. Iguchi, Y. Arai and M. Hayashi, Tetrahedron, 37, 4391 (1981); etc. However, in these cases, a mixture of 5-E isomer and 5-Z isomer is obtained as shown in the following reaction scheme and it is very difficult under the present situation to separate only the 5-E isomer useful as a pharmaceutical from such a mixture. ##STR6##